indium

In. Atomic number 49. A metal element in group 13 of the periodic table with the electron configuration [Kr]4d ¹⁰ 5s ² 5p ^1. The element's name comes from the indigo color of its atomic emission spectrum. It was discovered in sphalerite by F. Reich and HT Richter of Germany in 1863. Atomic weight 114.818(3). There are two natural isotopes with mass numbers 113 (4.29(5)%) and 115 (95.71(5)%), the latter of which is a radioactive isotope that emits 0.496 MeV beta rays and has a long half-life of 4.41×10 ¹⁴ y. Radioactive nuclides with mass numbers between 98 and 134 are known.
Abundance in the earth's crust is 0.1 ppm. It is obtained during the refining of lead and zinc ores. The metal is produced by electrolytic reduction from aqueous solutions of cyanides and other compounds. It is one of the rare metals and its depletion is a concern. The main producing countries are Canada and China, but it is imported from China, Korea, Canada, and the United States, in that order. In Japan, the Toyoha Mine near Jozankei produced the highest quality crude ore, but it closed in March 2006 due to the exhaustion of ore reserves. The world's largest demand (888 t, 2006) is met by the by-product of imported zinc concentrate and recovery from recycled home appliances. A soft silvery-white metal. Melting point 156.61 °C, boiling point 2080 °C. Density 7.31 g cm ^-3 (20 °C). Standard electrode potential In ³⁺ /In-0.3382 V. First ionization energy 5.786 eV. Chemically, it is resistant to alkaline solutions, but is easily attacked by acids. There are In ^I and In ^III compounds, and In ^I compounds have a strong reducing effect. Indium shows a vivid indigo flame reaction, and spectral emission lines at wavelengths of 451.155 and 410.195 nm are used for analysis. Historically, indium was widely used as a material for bearing alloys, taking advantage of its low melting point and plasticity, but currently its largest use is in ITO transparent electrodes for liquid crystal displays, which accounts for more than 95% of the use in Japan (as of 2006), as well as in light-emitting diodes and other compound semiconductor materials, low-melting-point alloys, and glass sealing alloys. It is not particularly toxic, but it is designated as a Class 2 chemical substance under the PRTR Law, and is classified as Work Environment Class 2 (1 mg m ^-3 or less (gas), 0.1 mg m ^-3 or less (particulate matter)). [CAS 7440-74-6]

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

In．原子番号49の元素．電子配置[Kr]4d¹⁰5s²5p¹の周期表13族金属元素．元素名は原子輝線スペクトルのインジゴ色から命名された．1863年，ドイツのF. ReichとH.T. Richterがせん亜鉛鉱中に発見した．原子量114.818(3)．天然には，質量数113(4.29(5)％)と115(95.71(5)％)の2種の同位体が存在し，後者は，4.41×10¹⁴ y という永い半減期をもつ，0.496 MeV のβ線を放出する放射性同位体である．質量数98～134の放射性核種が知られる．
地殻中の存在度0.1 ppm．鉛や亜鉛鉱の精錬の際に得られる．金属はシアン化物などの水溶液から電解還元してつくられる．資源的にレアメタルの一つで枯渇が心配されている．主要産出国はカナダ，中国であるが，輸入先は中国，韓国，カナダ，アメリカの順である．わが国では，定山渓近くの豊羽鉱山は最高品位の粗鉱を産出していたが，鉱量枯渇で2006年3月閉山．輸入亜鉛精鉱の副産物と家電製品リサイクルからの回収で世界最大の需要(888 t，2006年)をまかなっている．軟らかい銀白色の金属．融点156.61 ℃，沸点2080 ℃．密度7.31 g cm^－3(20 ℃)．標準電極電位 In^3＋/In－0.3382 V．第一イオン化エネルギー5.786 eV．化学的にはアルカリ溶液に対しては抵抗を示すが，酸には容易に侵される．化合物は In^Ⅰと In^Ⅲ化合物があるが，In^Ⅰ化合物は強い還元作用をもつ．インジウムはあざやかな藍色(インジゴ)の炎色反応を示し，分析には波長451.155，410.195 nm のスペクトル輝線が用いられる．歴史的には，低融点，可塑性を利用して軸受け・ベアリング用合金の材料としての用途が大きかったが，現在の最大の用途は液晶ディスプレイ用のITO透明電極でわが国では95％ 以上(2006年)，そのほか，発光ダイオードなど，化合物半導体の材料，低融点合金，ガラス封着用合金の材料などに用いられる．毒性はとくに高くはないが，PRTR法・第二種化学物質として，作業環境クラス2(1 mg m^－3 以下(気体)，0.1 mg m^－3 以下(粒子状物質))の指定を受けている．[CAS 7440-74-6]

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